Such an exhaust line is provided to equip an internal combustion engine, for example a diesel engine. It includes a catalyst provided to reduce the nitrogen oxides and an injector placed upstream from the catalyst. The injector is designed to inject a reagent, in particular a reducing agent or substance producing a reducing agent of the nitrogen oxides, such as urea, in the exhaust line. The urea consecutively undergoes two chemical reactions, thermolysis and hydrolysis, and is converted into ammonia. Within the catalyst and when the exhaust gases reach a certain temperature, the ammonia reacts chemically with the nitrogen oxides, reducing them into nitrogen and water.
In an exhaust line including an SCR system, i.e., the catalyst performing the selective reduction of the nitrogen oxides, the injection of the reducing agent is generally located downstream from the mechanical decoupling element to prevent damaging the latter, for example to avoid the risks of corrosion and mechanical failure. Such an arrangement nevertheless has the major drawback of increasing the startup time for the conversion of nitrogen oxides due to the distance of the SCR system from the engine.
In light of the aforementioned constraints, the architecture of such an exhaust line including an SCR system makes it more difficult to obtain an effective increase in the conversion of nitrogen oxides NOx when the vehicle is traveling under urban conditions, as it is not possible to reach the threshold or minimum temperature authorizing the injection of the reducing agent quickly.
In this context, the invention aims to propose an exhaust line whereof the operation is more satisfactory, with a more effective conversion of the nitrogen oxides.